salt will increase fish mucuse combined with blue or green dayly water changes and and high temp will work.
I keep nothobranchus killies and my water has little / no buffer in it , this can aloue swings in the ph ,notho's can get velvet, very much like white spot .
i treat this as follows
methyline blue , temp 26C , 25% water change every day with blue top up ,and 1tp per 4lt's( if it's bad 1.5tp per 4lt)and it works fast , fish back breeding in 1.5 weeks. a 25% water change dayly is xtrem os i dont advise it to others cus there not my fish .
but when white spot gets bad it can kill so fast you dont want to muk around .